The major endeavor of this project is to characterize the pharmacological actions of the endogenous cannabinoids and to identify commonalities and differences between TEC and the endogenous cannabinoids. We plan to prepare and evaluate metabolically stable and potent analogs of 2-arachidonyl-glycerol that will greatly enhance our ability to fully characterize the pharmacological properties of this compound. We will fully characterize the pharmacological properties of Professor Mechoulam's newest endocannabinoid, noladin ether, as well as other endocannabinoids as they are discovered. We propose to continue structure-activity relationship studies to gain a better understanding of how anandamide and other endocannabinoids interact with cannabinoid receptors. While it is clear that anandamide acts at CB1 receptors, there is mounting evidence that anandamide and its structural analogs may also interact at non-CB1 receptors to produce some of their pharmacological effects. One of our objectives is to establish the structural requirements for analogs that produce cannabinoid effects at non-CB1, non-CB2 receptors. The vanilloid VR1 receptor is one possible site of action we will investigate. Another important goal of our structure-activity relationship studies is to develop selective inhibitors for the anandamide membrane transporter and fatty acid amidohydrolase (FAAH). These selective probes will allow us to assess the importance of these two processes in the endocannabinoid system. We will also pursue new leads in the structure-activity relationships of SR 141716A in order to delineate between recognition and activation sites of the receptor. These studies may provide insights into the development of antagonists for the putative non-CB1 cannabinoids receptors, such as the VR1 receptor, and antagonists with an eicosanoid structure. Furthermore, antagonists devoid of inverse agonist proper-ties may also emerge which are critical for assessment of basal tone in the endocannabinoid system. Analogs and endogenous cannabinoids will continue to be provided by Drs. Razdan and Mechoulam, and we will systematically evaluate them for CB1 and CB2 receptor affinity, activation of 35S-GTPgS binding, potency in the mouse tetrad assay, and in drug discrimination. We will identify lead compounds for further evaluation as potential transporter and FAAH inhibitors and VR1 agonists by Dr. Pertwee and for activation of signal transduction pathways by Dr. Dewey. We will continue studies to determine whether differences between anandamide and THC are due to pharmacokinetic or pharmacodynamics factors through the use of FAAH knockout mice, site-specific drug injections to minimize metabolism, and metabolic inhibitors. All of these approaches are designed to systematically manipulate the endogenous cannabinoid system in order to more fully understand its physiological role, particularly its relationship to drug abuse.